Quantitative CMV PCR in stem cell transplant patients: DNA manual extraction versus automatic extraction

Abstract number: P1134

Cardeñoso L., Navarro J., Azcona J., Arenal N., Lomas E., Sanchez P., Camara R.

Introduction: The success of preemptive treatment of CMV infection in stem cell transplant (SCT) recipients before disease progress depends on efficient early diagnostic tests. The aim of this study was to compare a commercial quantitative CMV-PCR assay with DNA automatic extraction (TNAI-PCR) versus manual extraction (CA-PCR) in the diagnosis of CMV infection in our allogeneic STC recipients, comparing the results obtained by PCR with those obtained by antigenaemia (pp65).

Methods: All patients were prospectively monitored post-SCT with antigenaemia (pp65) CINApool^® (Argene) and Cobas Amplicor CMV Monitor Test^® (Roche) (DNA manual extraction, CA-PCR). A total of 211 blood samples obtained between January 2005 and May 2006 corresponding to 45 CMV infection episodes from 24 SCT patients, were tested retrospectively using COBAS Ampliprep TNAI kit^® (Roche) (DNA automatic extraction system, TNAI-PCR).

An episode is defined since the first positive sample by any method until the first negative sample by both techniques. A positive sample was defined by antigenaemia 2 cel/4×10⁵ cel and/or PCR 600 copies/mL. Repeated positive samples were considered the same episode. Independent episodes in one individual were considered if there were at least 15 days of negative serial detections. Samples and episodes were analysed independently. Concordance between methods was determined by Kappa and Spearman coefficients. P-values lower than 0.05 were considered statistically significant.

Results: Good correlation was found between CA-PCR and TNAI-PCR (Spearman coefficient=0.8, p < 0.001). Assuming qualitative interpretation of PCR, good concordance was also found between CA-PCR and TNAI-PCR (Kappa index=0.6, p < 0.001).

Episodes analysis: As a whole, TNAI-PCR detected 39 out off 45 episodes (86.7%) and by CA-PCR 32 out off 45 episodes (71.1%) (p = 0.07).

Twenty out off 45 episodes (44.4%) were detected by both techniques at the same time. Five episodes (11.1%) were detected only by antigenaemia, 8 episodes (17.8%) by TNAI-PCR only and 1 episode (2.2%) by CA-PCR.

In 24.4% episodes, TNAI-PCR was earlier than CA-PCR (median = 34 days). Thus in 42.2% (24.4%+17.8%) episodes TNAI-PCR improved CMV detection versus CA-PCR.

Conclusion: Automatic extraction improves sensibility detecting positive samples and lowers CMV infection diagnosis delay time in SCT patients. But in this moment, pp65 antigen detection cannot be replaced by all biological molecular methods.